Abstract
Background
Small fiber neuropathy (SFN) affects thinly myelinated and unmyelinated fibers, often
presenting with subtle clinical signs that are undetectable in routine nerve conduction
studies. Vitamin B12 deficiency is a known risk factor for SFN, yet early-stage cases
frequently remain undiagnosed. Sympathetic skin response (SSR) and cutaneous silent
period (CSP) are noninvasive electrophysiological techniques used to assess autonomic
and somatic small fiber function.
Objective
The present study aimed to evaluate the diagnostic utility of SSR and CSP in detecting
possible subclinical small-fiber neuropathy (pSFN) in individuals with early-stage
vitamin B12 deficiency.
Methods
The present observational study included 28 patients with vitamin B12 deficiency who
had nonspecific complaints, Douleur Neuropathique en 4 Questions (DN4) scores < 4,
and normal nerve conduction studies, along with 25 healthy controls. Electrophysiological
testing involved SSR recordings from all extremities and CSP measurements from the
right median and sural nerves.
Results
In the patient group, Median Nerve Cutaneous Silent Period (MN-CSP) and Tibialis Anterior
-Sural Cutaneous Silent Period (TA-sural CSP) durations were significantly shorter,
while termination and onset latencies were prolonged compared with controls. MN-CSP
and TA-sural CSP durations demonstrated high diagnostic accuracy. Sympathetic skin
response latencies were significantly prolonged in both hands and feet, indicating
autonomic dysfunction. No significant differences were observed in SSR amplitudes.
Conclusion
Sympathetic skin response and CSP are valuable tools for detecting possible subclinical
SFN in vitamin B12 deficiency. Sympathetic skin response effectively identified autonomic
dysfunction, while CSP provided additional diagnostic value for somatic small fiber
impairment. Combining SSR and CSP may enhance early detection of pSFN in vitamin B12
deficiency and allow timely intervention.
Keywords
Vitamin B 12 Deficiency - Small Fiber Neuropathy - Galvanic Skin Response - Reflex,
Abnormal - Electrodiagnosis
Bibliographical Record
Elif Simin Issi. Assessment of possible small fiber Neuropathy in early-stage vitamin
B12 deficiency using electrophysiological methods. Arq Neuropsiquiatr 2025; 83: s00451811722.
DOI: 10.1055/s-0045-1811722
